Pass over present that may divert sailors (12)
I believe the answer is:
crosscurrent
'that may divert sailors' is the definition.
(a crosscurrent may throw sailors off course)
'pass over present' is the wordplay.
'pass over' becomes 'cross' (synonyms).
'present' becomes 'current' (similar in meaning).
'cross'+'current'='CROSSCURRENT'
(Other definitions for crosscurrent that I've seen before include "A tendency in conflict with another" , "Conflicting flow" , "Flow at an angle to the main flow" .)